Advanced glycosylation endproducts (AGEs) represent a heterogeneous class of reactive products which form spontaneously in vivo from the non-enzymatic reaction of glucose and proteins (Monnier et al., 1981, Science 211:491; Bucala et al., 1992, Advanced glycosylation endproducts, Harding and Crabbe, eds., In Post-Translational Modifications of Proteins, CRC Press Inc. 2: 53-79). Glucose and other reducing sugars react non-enzymatically with the amino groups of proteins in a concentration-dependent manner. Over time, these initial Amadori adducts undergo further rearrangements, dehydrations and cross-linking with other proteins to accumulate as a family of complex structures which are referred to as Advanced Glycosylation Endproducts (AGEs). Although this chemistry has been studied by food chemists for many years, it was only in the past decade that the presence of AGEs in living tissue has been established. The excessive deposition of these products on structural proteins as a function of age and elevated glucose concentration, taken together with evidence of effective prevention of tissue pathology by an AGE inhibitor, aminoguanidine, has lent support to the hypothesis that the formation of AGEs plays a role in the long term complications of aging and diabetes.
In vivo formation of AGE-proteins proceeds slowly under normal ambient glucose concentrations, while the rate of AGE accumulation is markedly accelerated in the presence of hyperglycemia, as occurs in diabetes mellitus (Monnier and Cerami, 1983, Biochim. Biophys. Acta 760:97-103; Monnier et al., 1984, Proc. Natl. Acad. Sci. USA 81:583-87). Numerous studies suggest that AGEs play an important role in the structural and functional alterations which occur in senescence and long-term diabetes (Brownlee et al., 1988, N. Engl. J. Med. 318:1315-21).
Increased levels of AGEs in tissue and serum of hyperglycemic patients have been pathogenetically linked to numerous diabetic complications, such as vascular damage and nephropathy (Vlassara et al., 1994, Lab. Invest. 70:138). Diabetic patients also exhibit increased susceptibility to bacterial infections; however, early studies failed to demonstrate a significant adverse effect of diabetes-associated metabolic disturbances, e.g. hyperglycemia, on defense system function or bacterial growth (Moutshen et al., 1992, Diabetes and Metabolisme 18:187). We hypothesize that elevated levels of AGE may serve as a mediator to suppress normal defense in diabetic patients.
More generally, research on the binding properties and receptors for AGE-modified proteins has not heretofore identified a particular binding domain or motif responsible for AGE recognition, contact or binding. It is appreciated that such a discovery would greatly facilitate the development of effective strategies for both diagnostic and therapeutic modalities to deal with the adverse sequelae that have observed and extensively reported. It is therefore toward such a discovery that the present invention is directed.